It seems like every single attempt I've made at making a Thai-style coconut curry ends up with the sauce mixture separating. Although it usually still tastes good, the coconut ends up looking like it has curdled.

My question is what could I be doing wrong? I've mainly been following the recipe on the side of the curry paste I have (Thai Kitchens brand, IIRC).

Stir some of the paste with a can of coconut milk (I've been using Chao Koh) until that boils.

Add some fish sauce and chicken broth along with the meat and vegetables

Simmer until cooked.

My suspicion is I may be using too much chicken stock. I usually use about 1-2 cups. The vegetables I add(typically bell peppers and onions) will also contribute additional liquid to the curry.

My family and I love this dish, but I would really like to perfect its preparation. What steps can I take to prevent the coconut milk from separating from the curry?

13 Answers
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Even though it isn't really milk (in the dairy sense), coconut milk still naturally separates into a thick cream and thinner liquid like regular milk. As such, when working with coconut milk you should still follow the same procedures you would to make a milk-based cream sauce.

The number one rule when making any creamy sauce is: DON'T LET IT BOIL! Boiling will guarantee that your creamy sauce (including sauces made with coconut milk) will break in some form or fashion. At most, you should cook these at a bare simmer.

Other than that, there are some techniques you can use to keep your curry smooth.

You could use an emulsifier like honey (common in vinaigrettes, where it is used to make sure the oil and vinegar don't separate), added toward the end of cooking.

You could also use a thickening agent, like a cornstarch slurry or a quick roux. Curry paste is also a thickening agent. As a general rule of thumb, when making Thai-style curry I usually cook my vegetables in a little more oil than I think they need, then add the curry paste and sauté that until it has absorbed the oil (along with any dry spices). It will act as a roux for the coconut milk and make sure there are no lumps in the final curry.

Lastly, cooking the curry uncovered at a simmer, stirring occasionally, will thicken it up nicely and help all the ingredients stay together.

The separation you are getting is caused by inadequate mixing of coconut solids and curry paste. This will happen if you add coconut cream at the wrong time (or the wrong way) and you then cook it incorrectly.

David Thompson is a world renowned chef and an expert on Thai cuisine. Here's my adaption of Thompson's technique:

Place 5 or so tablespoons of coconut cream into your pan and fry it until the clear oil separates from the solids. This happens when the most of the water has boiled out of it. If you don't shake the coconut milk before you open it then the cream will be at the top and it will save you time.

Once coconut cream has separated, stir in the curry paste and fry that until the oil starts to separate again.

Add the remainder of the coconut milk, stir to combine then season with fish sauce and palm sugar for saltiness and sweetness respectively.

Simmer until you are almost at the desired thickness. Steam or fry any vegetables you want in the curry during this time. How you cook them will depend on the texture you want. Vegetables, such as broccoli, can impart a bad taste to a curry if they are added raw.

When the curry is near to the desired thickness add any meat. The timing depends on the size of the meat and whether it has bones.

When meat is cooked through add the vegetables to reheat them.

Enjoy.

David Thompson also mentioned the following rules of thumb:

Green curries are on the sweet side of salt/sweet balance and red curries are on the salty side.

Use sweet vegetables in a salty curry and non-sweet (usually bitter) vegetables in a sweet curry. This is so you don't lose the curry's basic flavour profile in the taste of the other ingredients.

I live in Thailand and, unfortunately, most restaurants here don't even make their green curries sweet. The green curry pastes available at markets here are so salty and can't be counteracted by palm sugar. It's probably for preservation since the pastes are not in cans or packets.

Some people do argue that green curries shouldn't be sweet. Those in the know point towards the Thai name for a green curry: แกงเขียวหวาน (gaaeng khiiaw waahn). Directly translated: curry green sweet.

Nice thorough answer! There are many questions here about Thai cuisine, I hope you take the time to look at/answer more. Welcome to Seasoned Advice!
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JolenealaskaNov 24 '13 at 9:19

Thank you so much for the positive comment @Jolenealaska! I will definitely see what I can do about some other questions. Is there anything in particular that you could suggest?
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Sammy SpetsNov 24 '13 at 12:34

Nothing in particular, just that if Thai cuisine is a specialty, use the search engine to search for Thai. If anything else, technique or ingredient or whatever interests you, search for that. Read the FAQ under "about" and don't be shy! If you've got a question, ask, but I recommend reading the FAQ first. Again, welcome.
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JolenealaskaNov 24 '13 at 12:46

Dang. I'm going to have to try this then. Thanks!
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ddysartNov 25 '13 at 19:47

I'm disappointed to see the answers to your query. They're way off the mark.

OK - firstly, you want to get the oil to separate when cooking the coconut cream in Thai cooking. Without that, you end up with a smooth, creamy sauce which just isn't the authentic way to do it at all. That's the standard beginner's mistake. You can use the heavy cream (the harder top of an unshaken can of coconut milk) to start with, let it bubble so that the oil starts to separate. You can then add your paste and continue to fry it for a couple of minutes and then add the rest of the milk. Yes - you DO want the milk to boil lightly. You need to add the fish sauce at this point, anyway.

Plenty of authentic examples to show you the process on Videojug, if you want to take a look there.

But the OP wants that smooth creaminess - at least that seems pretty clear to me from the question. So, it doesn't really matter too much if it's authentic. Also, I'm not sure where you got that idea; it's a very common way to see curries prepared. Sure, it's not the only way, but it's perfectly authentic.
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hunter2Jun 25 '13 at 9:18

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@hunter2 I think this is still a valid point. If oil separation is normal, the recipes may be written to make it happen. This at least answers the "What am I doing wrong?" part of the question: nothing!
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SourDohAug 10 '13 at 20:23

If ever you need to add milk to a hot dish it is likely to either curdle or separate.
The trick is to take some of the hot liquid, a couple of spoons should do, and put it into a small bowl.
Now let it cool down a little.
Then you add the milk to the warm liquid in the small bowl and beat it with a fork. The two liquids should incorporate without separating.
You can then add this beaten liquid back to your hot dish while beating or stirring the gravy or curry all the time.
This technique works for both fresh and coconut milk as well as for yogurt.

I use the light coconut milk. I add a teaspoon and a half of corn flour to it with some suger. I stir fry the paste then add the meat and veggies. I then add some vegetable stock and let the mixture boil down before adding the corn flour milk mixture at the very end.

The answer was actually in the question. You use Chakoh milk and it's doing what it is supposed to do....split. It does this because it has no emulsifiers. Plenty of (inferior) brands around with emulsifiers that are less likely to split. There is a good explanaion here Cooking with Coconut Milk

I generally make my own curry paste, and it goes into the pan first after the oil is hot.
The vegetables/meat/other stuff go in afterwards.
Once those are all done to your satisfaction, you add the coconut milk.